The present invention relates to a carburation device in particular for internal combustion engines.
At present, such a kind of device substantially comprise the following elements: means for delivering the fuel at a metered rate relatively to combustion-supporting air according to the desired stoichiometric ratio; a supply duct for at least one from the following fluids: combustion-supporting air and combustible mixture obtained by mixing combustion-supporting air with fuel; and suitable means for varying the surface area of the internal bore of the feed duct in order to change the revolution speed of the engine with which the carburation device can be associated.
The feed duct can be co-axially constrained to the intake duct of the engine it is destined for. The suitable means for varying the surface area of the inner bore of the feed duct are presently constituted by throttle valves or guillotine valves which, by acting inside the feed duct, choke it as a function of the instantaneous performance required from the engine.
Unfortunately, some time ago it was discovered that such throttle or guillotine valves considerably disturb the fuel stream which consequently, by displaying irregularities from a fluid-dynamic point of view, generate drawbacks.
These drawbacks are well-known for those skilled in the art and therefore only the main ones of them are generally mentioned: lower torque at low revolution speed values, smaller power at high values of revolution speed values, and higher actual specific consumption than theoreticallly required.
At present, in order to at least partially obviate the above-mentioned drawbacks, the valve manufacturers give such throttle or guillotine valves such shapes as to limit as far as possible the fluid-dynamic disturbance caused by these valves, and design such valves for use in several engines based on target engine characteristics and envisaged usage.